Numerous stent designs are known in the art, of which self-expanding and balloon-expandable stents are the predominant commercially available types. Self-expanding stents, such as the stents described in U.S. Pat. No. 4,580,568 to Gianturco, generally provide good crush-resistance and axially flexibility, thus permitting delivery through tortuous anatomy, but provide lower radial strength once deployed. Balloon-expandable stents, such as the stents typified by U.S. Pat. No. 4,739,762 to Palmaz, provide high radial strength, but tend to have increased axial rigidity that affects deliverability through tortuous vessels. It has therefore been a goal of many expandable stent designs to enhance axial flexibility of the stent to improve deliverability, and thus the number of potential applications for the device, while retaining an acceptable level of radial strength.
Previously known stents are generally supplied in a variety of lengths and diameters, so the clinician can select the stent most appropriate for a specific patient. Such stents typically have homogeneous properties along the length of the stent and provide limited options for customization responsive to the needs of a particular patient.
In certain applications, the best solution for a particular patient would involve a combination of the mechanical and operating properties of both balloon-expandable and self-expanding stents. Therefore, it would be desirable to provide a modular stent that permits the clinician to “mix and match” stent modules to build a stent having specific characteristics tailored for a specific patient or application.
For example, it may be desirable to provide a stent having axial modules of variable rigidity and crush-resistance, such as for use in the carotid arteries. Due to the generally exposed nature of these arteries in the region of the neck, situations have been reported where balloon-expandable stents have been subjected to partial crushing. On the other hand, self-expanding stents are susceptible to migration. Therefore, it would be desirable in certain applications to provide a stent having a resilient, self-expanding central portion and balloon-expandable end regions that permit the stent to be anchored in position.
The ability to vary the mechanical properties of the stent also would permit a stent to include non-metallic components, such as biodegradable or bioabsorbable segments. This ability might prove particularly advantageous where it is desired to deliver a predetermined dose of drug to via drug-eluting segments, for example, by incorporating a specified number of drug-eluting segments into the prosthesis that eventually dissolve in the fluid stream through the vessel.
As yet another example, U.S. Pat. No. 6,048,361 to Von Oepen describes a stent designed for use in bifurcated vessels having a side branch aperture. As described in that patent, the stent is manufactured with fixed length regions proximal and distal to the aperture. Thus, the stent may not be suitable in some patients because the fixed length of the proximal or distal region may interfere with collateral vessels upstream or downstream of the bifurcation. Accordingly, it would be desirable to provide a vascular prosthesis that includes a side branch aperture, but which has proximal and distal regions that may be tailored for a specific patient.
U.S. Pat. No. 5,824,037 to Fogarty et al. describes a modular intralumenal prosthesis, such as for a stent-graft, that includes a plurality of modules having standard interface ends for engaging adjacent modules. The modules employed in the prosthesis may include variations in axial length, cross-section, perimeter, resilient expansive force and axial flexibility. The modules are “locked” together by stitching a liner material.
One drawback of the prosthesis described in the Fogarty et al. patent is that the prosthesis may lack structural rigidity in the expanded configuration. In particular, the patent describes no mechanism to positively engage the modules other than the liner material. It therefore would be desirable to provide a modular stent wherein the modules cannot be locked together without stitching or a liner material.
The foregoing patent also does not teach that a modular stent may be used to improve conformance of the stent to a patient's vasculature when used in a bifurcated region, or the desirability of intermixing segments including different materials, including bioabsorbable or drug-eluting segments.
Therefore, it would be desirable to provide a vascular prosthesis including a plurality of modular segments interconnected by lockable joints that enhance articulation between adjacent segments during delivery of the prosthesis and enhance structural rigidity of the prosthesis in the deployed configuration.
It also would be desirable to provide a vascular prosthesis that includes a plurality of modular segments interconnected by a plurality of joints, in which the modular segments include different materials or strut configurations, thereby permitting the structural rigidity of the vascular prosthesis in the deployed configuration to be tailored for a specific patient or application.
It further would be desirable to provide a vascular prosthesis including a plurality of modular segments, wherein one or more segments may be bioabsorbable or drug-eluting, to provide predetermined doses of drug to the vessel wall or intravascularly to a desired tissue region.
Still further, it would be desirable to provide a vascular prosthesis that includes a plurality of modular segments, wherein one or more segments of customizable length may be intermixed to provide a desired feature, for example for the treatment of bifurcated vessels or aneurysms.
Still further, it would be desirable to provide a method for assembling a device wherein a physician could intermix device components formed of one or more interlocking modular segments, in order to provide a vascular prosthesis with radial force and structural rigidity tailored to a specific patient or application.
Still further, it would be desirable to provide a method for assembling a device wherein a physician could intermix device components that include one or more interlocking modular segments to make a customizable vascular prosthesis by snapping the components together without the need for assembly tools.
Still further, it would be desirable to provide a system for assembling a device that includes interlocking modular segments and interlocking modular end segments that can be joined to form a device having a customizable length, configuration or structural rigidity.
It also would be desirable to provide device components that include modular segments configured to be welded together, so to eliminate the need for traditional laser cutting of long tubular members.